wayland: upgrade wayland-window (#339)

* wayland: upgrade wayland-window

This new version of wayland window considerably simplifies the
window handling for winit, meaning much of the previous juggling
is no longer needed, and the windows will appear even if nothing is
drawn.

* wayland: cleanup unused stuff

src/os/unix.rs

@@ -121,13 +121,11 @@ pub trait WindowExt {
 
     /// Check if the window is ready for drawing
     ///
-    /// On wayland, drawing on a surface before the server has configured
-    /// it using a special event is illegal. As a result, you should wait
-    /// until this method returns `true`.
+    /// It is a remnant of a previous implementation detail for the
+    /// wayland backend, and is no longer relevant.
     ///
-    /// Once it starts returning `true`, it can never return `false` again.
-    ///
-    /// If the window is X11-based, this will just always return `true`.
+    /// Always return true.
+    #[deprecated]
     fn is_ready(&self) -> bool;
 }
 
@@ -195,10 +193,7 @@ impl WindowExt for Window {
 
     #[inline]
     fn is_ready(&self) -> bool {
-        match self.window {
-            LinuxWindow::Wayland(ref w) => w.is_ready(),
-            LinuxWindow::X(_) => true
-        }
+        true
     }
 }